Method for using chunks of change log data for comparing a source and a target database which are actively being kept in synchronization with each other

Abstract

An automated method is provided for comparing a source database and a target database that are intended to be kept in synchronization with each other. An application processes transactions that are posted to the source database, and a synchronization process processes transactions that are posted to the target database. Change log data is chunked from a change log associated with the source database to create first chunks of change log data. Change log data is also chunked from a change log associated with the target database to create second chunks of change log data. A comparison engine compares representations of the first chunks of change log data with representations of the second chunks of change log data, wherein the second chunks of change log data correspond to the same respective first chunks of change log data that were made to the source database and kept in synchronization with the target database via the synchronization process. The source database and the target database are presumed to be in synchronization with each other via the synchronization process when the comparison indicates that the representations of the first chunks of change log data match the representations of the second chunks of change log data. The source database and the target database are presumed not to be in synchronization with each other when the comparison indicates that the representations of the first chunks of change log data do not match the representations of the second chunks of change log data. An action is performed when the comparison indicates that the representations of the first chunks of change log data do not match the representations of the second chunks of change log data. The action may be a corrective action that resynchronizes the target database with the source database, or that suspends or stops the application from processing transactions.

What is claimed is: 
     
         1 . An automated method for comparing a source database and a target database that are intended to be kept in synchronization with each other, wherein an application processes transactions that are posted to the source database, and wherein a synchronization process processes transactions that are posted to the target database, the method comprising:
 (a) chunking change log data from a change log associated with the source database to create first chunks of change log data;   (b) chunking change log data from a change log associated with the target database to create second chunks of change log data;   (c) comparing, in a comparison engine, representations of the first chunks of change log data with representations of the second chunks of change log data,
 wherein the second chunks of change log data correspond to the same respective first chunks of change log data that were made to the source database and kept in synchronization with the target database via the synchronization process, and 
 wherein the source database and the target database are presumed to be in synchronization with each other via the synchronization process when the comparison indicates that the representations of the first chunks of change log data match the representations of the second chunks of change log data, and wherein the source database and the target database are presumed not to be in synchronization with each other when the comparison indicates that the representations of the first chunks of change log data do not match the representations of the second chunks of change log data; and 
   (d) performing an action when the comparison indicates that the representations of the first chunks of change log data do not match the representations of the second chunks of change log data.   
     
     
         2 . The method of  claim 1  wherein the action is a corrective action that resynchronizes the target database with the source database. 
     
     
         3 . The method of  claim 1  wherein the action is a corrective action that suspends or stops the application from processing transactions. 
     
     
         4 . The method of  claim 1  wherein the representations of the changes in the first and second chunks of change logs are hash values of their respective changes. 
     
     
         5 . The method of  claim 1  wherein the representations of the changes in the first and second chunks of change logs are hash values of batches of their respective changes. 
     
     
         6 . The method of  claim 1  wherein the representations of the changes in the first and second chunks of change logs represent completed steps or operations of the transactions. 
     
     
         7 . The method of  claim 1  wherein the source and target databases include rows of data which are modified by the transactions, and wherein the representations of the changes in the first and second chunks of change logs are before and/or after images of the rows of data which were modified by the transactions. 
     
     
         8 . The method of  claim 1  wherein the changes made to the source database are replicated to the target database from the first chunks of change log. 
     
     
         9 . The method of  claim 1  wherein the changes made to the source database are replicated to the target database using dual writes. 
     
     
         10 . The method of  claim 1  wherein the synchronization process is a replication process that replicates transactions that are posted to the source database to the target database. 
     
     
         11 . The method of  claim 1  wherein the synchronization process is an application that processes transactions to the target database that are posted to the source database.